Water is becoming a scarce resource in parts of the world and proper water management is becoming an important focus area in order to feed a growing world population. In addition, it is vital to apply plant nutrients and additives according to crop needs and it is well documented that the use of irrigation water as the delivery system for plant nutrients (fertigation) optimises the total crop performance (see for example U.S. Pat. No. 7,937,187, FW Enviro, LLC, May 2011). Among others, the benefits of fertigation include: 1) a uniform application in the form of uniform distribution and precision placement of input matter, such as fertilizers and crop supplements; 2) timely application wherein the input matter can typically be applied regardless of weather or field conditions; 3) reduced application costs such that the cost of application is about one-third the cost of conventional application methods; 4) improved crop management using timely applications of small but precisely delivered amounts of input matter directly to the root zone allows growers to effectively manage input matter programs, which conserves input matter, saves money, and optimizes yield and quality; 5) reduced soil compaction by reduced tractor and equipment traffic in fields; 6) minimizes exposure of workers to chemicals through reduced operator handling, mixing and dispensing of potentially hazardous matters with people and non-target crops not being exposed to inadvertent chemical drifts; 7) reduced environmental contamination when fertigation devices used are properly designed and calibrated including having the recommended safety devices to help preserve the quality of the environment; 8) marginal farming areas can be fertilized after the crops have emerged from the ground rather than adding input matter prior to crop emergence and wasting money on unused supplement.
A common fertigation system usually comprises a set of pressurized tubes to carry the water to the crops, drip and/or spray devices to dispense the water to the crops, a storage and dosage facility for the crop input matter (usually a fertilizer), the necessary pumps, valves and sensors and a central processing unit controlling the system.
The fertilizer can be added to the water on a continuous basis at concentrations and fertilizer ratios which are fit for the current grow stage of the crop. This is a common practice in intensive cropping systems where the fertilizer is applied at concentrations typically 0.1-0.05 weight % into the water, reaching the crops. However, care needs to be taken that the total amount of undissolved particulates is low, as a too high amount may clog and block the drip and/or spray devices and reduce the efficiency of the fertigation system.
In prior art fertigation systems, such as the one described in U.S. Pat. No. 7,937,187, in a first step, a concentrated liquid fertilizer solution or dry water soluble particles are first dissolved into a concentrated stock solution (typically 10-30%) which is subsequently diluted (typically at ratio 1:100) and, in a second step, injected into the pressurized water system by a pump or Venturi-type system to accommodate the right concentration for plant requirements. The prior art system is labour-intensive and demands repetitive work processes to dissolve and prepare the stock solution from the bulk particulate matter. As the bulk of the fertilizers are available in solid, particulate form, in the case of applying soluble input matter, it would be of interest to combine the dissolving and injection step in a combined dissolving and injector unit, and hence to directly use the dry particulate solids in the fertigation system without a step of dissolving said particulate solids, in particular fertilizers, first into a stock solution, usually done manually.
EP 1 749 443 discloses a sprayer having a remixing chamber (I, II) provided for remixing and for converting the granulated or powdered active component into liquid form. The remixing chamber is connected by a connection line (12) with container (1) for receiving the carrier fluid. The remixing chamber is connected with container (9) containing active component by another connection line (10, 18). Remixing chamber is connected with mixing chamber (5) by connection line (16, 17).
U.S. Pat. No. 6,173,732 discloses a chemical feeding system for adding either liquid or 100% water soluble solid chemicals including fertilizer, insecticide and a herbicide to a lawn sprinkler system either above or below ground level. The system has one or two vertically oriented mixing chambers containing a removable sponge filter. An effluent tube is attached to the bottom of the mixing chamber for recycling through an adjustable flow meter valve. A drain tube with a shutoff valve and a one-way check valve leads to the main sprinkler system.
US 2004/0042335 discloses an apparatus and method for introducing a dry material into a fluid stream in a way that ensures a predictable, highly accurate and consistent application of the material where the fluid stream may be fixed or variable, where the material is handled and metered in dry bulk form and may be highly soluble or nearly insoluble, and in a manner that continuously and automatically adjusts the application rate to compensate for varying material bulk density, as well as, and in addition to, varying fluid flow rates or chemical composition, in order to provide a precise fluid treatment level at all times. The present invention incorporates the necessary means to store large quantities of the dry process amendment as an integrated and dust-free function of the apparatus and process, and is capable of monitoring and adjusting material levels and introduction rates in real time in response to variations in density, fluid flow rate and/or chemistry composition.
EP 2 289 301 A1 (Melcart Projects, March 2011) describes a combined dissolution and injection system for solid particulate fertilizer, for use in the gardening/hobby sector, wherein the solid fertilizer is provided in an hermetically closed container, which is subsequently connected to the fertigation system by puncturing the bottom, filled with pressurized water from a bypass from an irrigation pipeline, and which injects its content through a Venturi-type injector into the irrigation pipeline at a constant pressure. Such system is not suitable for injection different amounts of fertilizer, different types of fertilizers or mixtures of different types of fertilizers and at varying rates. Furthermore, this device is operating only on the pressure side, such that it is necessary to pressurize the whole container up to the operating pressure of the irrigation pipeline.
US 2002/0186614 A1 (J. P. Millward, December 2002) describes a dissolution system for solid particulate fertilizer comprising a hopper which comprises an inverted perforated funnel the walls of which are sprayed on the inside with water such that particles of the feed present on the outside of said funnel are washed through the perforated funnel, forming a slurry in a slurry pan below the funnel, wherein the content of the pan is continuously pumped into an irrigation pipeline. Such system is very cumbersome to build and maintain.
There is a need for a fertigation system which utilizes particulate input matter as a feed, which is easy to operate in a continuous way, and which eliminates or at least reduces the amount of undissolved particles into the fertigation system.